RFID reader architecture

ABSTRACT

A highly integrated and low-cost reader for a radio frequency identification (RFID) system is realized by providing a transmitter operable to generate an outbound radio frequency (RF) signal and a receiver operable to receive an inbound RF signal having a frequency similar to a frequency of the outbound RF signal on a single integrated circuit. Since the inbound RF signal may include not only a modulated RF signal produced by an RFID tag responsive to the outbound RF signal, but also a blocking signal corresponding to the outbound RF signal, the receiver additionally includes a block cancellation module operable to substantially cancel the blocking signal from the inbound RF signal using the outbound RF signal and to substantially pass the modulated RF signal before down-conversion of the modulated RF signal.

CROSS REFERENCE TO RELATED PATENTS

This U.S. application for patent claims the benefit of the filing dateof U.S. Provisional Patent Application entitled, RFID READERARCHITECTURE, Attorney Docket No. BP5174, having Ser. No. 60/778,520,filed on Mar. 2, 2006, which is incorporated herein by reference for allpurposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

NOT APPLICABLE

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

NOT APPLICABLE

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention is related generally to radio-frequency identification(RFID) systems, and more particularly to RFID readers.

2. Description of Related Art

A radio frequency identification (RFID) system generally includes areader, also known as an interrogator, and a remote tag, also known as atransponder. Each tag stores identification data for use in identifyinga person, article, parcel or other object. RFID systems may use activetags that include an internal power source, such as a battery, and/orpassive tags that do not contain an internal power source, but insteadare remotely powered by the reader.

Communication between the reader and the remote tag is enabled by radiofrequency (RF) signals. In general, to access the identification datastored on an RFID tag, the RFID reader generates a modulated RFinterrogation signal designed to evoke a modulated RF response from atag. The RF response from the tag includes the coded identification datastored in the RFID tag. The RFID reader decodes the coded identificationdata to identify the person, article, parcel or other object associatedwith the RFID tag. For passive tags, the RFID reader also generates anunmodulated, continuous wave (CW) signal to activate and power the tagduring data transfer.

RFID systems typically employ either far-field technology, in which thedistance between the reader and the tag is great compared to thewavelength of the carrier signal, or near-field technology, in which theoperating distance is less than one wavelength of the carrier signal, tofacilitate communication between the RFID reader and RFID tag. Infar-field applications, the RFID reader generates and transmits an RFsignal via an antenna to all tags within range of the antenna. One ormore of the tags that receive the RF signal responds to the reader usinga backscattering technique in which the tags modulate and reflect thereceived RF signal. In near-field applications, the RFID reader and tagcommunicate via mutual inductance between corresponding reader and taginductors.

Currently, RFID readers are formed of separate and discrete componentswhose interfaces are well-defined. For example, an RFID reader mayconsist of a controller or microprocessor implemented on a CMOSintegrated circuit and a radio implemented on one or more separate CMOS,BiCMOS or GaAs integrated circuits that are uniquely designed foroptimal signal processing in a particular technology (e.g., near-fieldor far-field). However, the high cost of such discrete-component RFIDreaders has been a deterrent to wide-spread deployment of RFID systems.In addition, there are a number of different RFID standards, eachdefining a different protocol for enabling communication between thereader and the tag. Discrete RFID reader designs inhibit multi-standardcapabilities in the reader.

Therefore, a need exists for a highly integrated, low-cost RFID reader.In addition, a need exists for a multi-standard RFID reader.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theDrawings, the Detailed Description of the Invention, and the claims.Other features and advantages of the present invention will becomeapparent from the following detailed description of the invention madewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an RFID system in accordance withthe present invention;

FIGS. 2A and 2B are schematic block diagrams of an RFID reader inaccordance with the present invention;

FIGS. 3A-3D are schematic block diagrams of a transmitter of the RFIDreader in accordance with the present invention;

FIGS. 4A and 4B are schematic block diagrams of a multi-antennatransmitter of the RFID reader in accordance with the present invention;

FIG. 5 is a schematic block diagram of a receiver of the RFID reader inaccordance with the present invention;

FIG. 6 is a diagram illustrating an example of the functionality of theblock cancellation module of FIG. 5;

FIGS. 7A and 7B are schematic block diagrams of a dual-mode RF front endof the RFID reader in accordance with the present invention;

FIG. 8 is a schematic block diagram of a multi-band synthesizer of theRFID reader in accordance with the present invention;

FIG. 9 is a functional diagram of a multi-standard processor firmware ofthe RFID reader in accordance with the present invention; and

FIG. 10 is a logic diagram of a method for operating the RFID reader inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an RFID (radio frequencyidentification) system that includes a computer/server 12, a pluralityof RFID readers 14-18 and a plurality of RFID tags 20-30. The RFID tags20-30 may each be associated with a particular object for a variety ofpurposes including, but not limited to, tracking inventory, trackingstatus, location determination, assembly progress, et cetera. The RFIDtags may be active devices that include internal power sources orpassive devices that derive power from the RFID readers 14-18.

Each RFID reader 14-18 wirelessly communicates with one or more RFIDtags 20-30 within its coverage area. For example, RFID tags 20 and 22may be within the coverage area of RFID reader 14, RFID tags 24 and 26may be within the coverage area of RFID reader 16, and RFID tags 28 and30 may be within the coverage area of RFID reader 18. In one embodiment,the RF communication scheme between the RFID readers 14-18 and RFID tags20-30 is a backscatter technique whereby the RFID readers 14-18 requestdata from the RFID tags 20-30 via an RF signal, and the RF tags 20-30respond with the requested data by modulating and backscattering the RFsignal provided by the RFID readers 14-18. In another embodiment, the RFcommunication scheme between the RFID readers 14-18 and RFID tags 20-30is an inductance technique whereby the RFID readers 14-18 magneticallycouple to the RFID tags 20-30 via an RF signal to access the data on theRFID tags 20-30. In either embodiment, the RFID tags 20-30 provide therequested data to the RFID readers 14-18 on the same RF carrierfrequency as the RF signal.

In this manner, the RFID readers 14-18 collect data as may be requestedfrom the computer/server 12 from each of the RFID tags 20-30 within itscoverage area. The collected data is then conveyed to computer/server 12via the wired or wireless connection 32 and/or via peer-to-peercommunication 34. In addition, and/or in the alternative, thecomputer/server 12 may provide data to one or more of the RFID tags 2030 via the associated RFID reader 14-18. Such downloaded information isapplication dependent and may vary greatly. Upon receiving thedownloaded data, the RFID tag can store the data in a non-volatilememory therein.

As indicated above, the RFID readers 14-18 may optionally communicate ona peer-to-peer basis such that each RFID reader does not need a separatewired or wireless connection 32 to the computer/server 12. For example,RFID reader 14 and RFID reader 16 may communicate on a peer-to-peerbasis utilizing a back scatter technique, a wireless LAN technique,and/or any other wireless communication technique. In this instance,RFID reader 16 may not include a wired or wireless connection 32 tocomputer/server 12. In embodiments in which communications between RFIDreader 16 and computer/server 12 are conveyed through the wired orwireless connection 32, the wired or wireless connection 32 may utilizeany one of a plurality of wired standards (e.g., Ethernet, fire wire, etcetera) and/or wireless communication standards (e.g., IEEE 802.11x,Bluetooth, et cetera).

As one of ordinary skill in the art will appreciate, the RFID system ofFIG. 1 may be expanded to include a multitude of RFID readers 14-18distributed throughout a desired location (for example, a building,office site, et cetera) where the RFID tags may be associated withequipment, inventory, personnel, et cetera. In addition, it should benoted that the computer/server 12 may be coupled to another serverand/or network connection to provide wide area network coverage.

FIGS. 2A and 2B are schematic block diagrams of an RFID reader 14-18that includes an integrated circuit 56 and may further include a hostinterface module 54. By integrating the RFID reader 14-18 onto a singleintegrated circuit 56, the cost of the RFID reader 14-18 issignificantly reduced. As shown in FIGS. 2A and 2B, the integratedcircuit 56 includes a protocol processing module 40, an encoding module42, an RF front-end 46, a digitization module 48, a predecoding module50 and a decoding module 52, all of which together form the essentialcomponents of the RFID reader 14-18. In FIG. 2A, the integrated circuit56 further includes a digital-to-analog converter (DAC) 44, whereas inFIG. 2B, the DAC 44 is removed from the transmit path. Thus, in FIG. 2B,the power amplifier in the RF front end 46 takes digital power controlinput. The host interface module 54 may include a communicationinterface to a host device, such as a USB dongle, compact flash orPCMCIA.

The protocol processing module 40 is operably coupled to prepare datafor encoding in accordance with a particular RFID standardized protocol.In an exemplary embodiment, the protocol processing module 40 isprogrammed with multiple RFID standardized protocols to enable the RFIDreader 14-18 to communicate with any RFID tag, regardless of theparticular protocol associated with the tag. In this embodiment, theprotocol processing module 40 operates to program filters and othercomponents of the encoding module 42, decoding module 52, pre-decodingmodule 50 and RF front end 46 in accordance with the particular RFIDstandardized protocol of the tag(s) currently communicating with theRFID reader 14-18.

In operation, once the particular RFID standardized protocol has beenselected for communication with one or more RFID tags, the protocolprocessing module 40 generates and provides digital data to becommunicated to the RFID tag to the encoding module 42 for encoding inaccordance with the selected RFID standardized protocol. By way ofexample, but not limitation, the RFID protocols may include one or moreline encoding schemes, such as Manchester encoding, FM0 encoding, FM1encoding, etc. Thereafter, in embodiments in which the integratedcircuit 56 includes DAC 44, as shown in FIG. 2A, the digitally encodeddata is provided to the digital-to-analog converter 44 which convertsthe digitally encoded data into an analog signal. The RF front-end 46modulates the analog signal to produce an RF signal at a particularcarrier frequency that is transmitted via antenna 60 to one or more RFIDtags.

The RF front-end 46 further includes transmit blocking capabilities suchthat the energy of the transmitted RF signal does not substantiallyinterfere with the receiving of a back-scattered or other RF signalreceived from one or more RFID tags via the antenna 60. Upon receivingan RF signal from one or more RFID tags, the RF front-end 46 convertsthe received RF signal into a baseband signal. The digitization module48, which may be a limiting module or an analog-to-digital converter,converts the received baseband signal into a digital signal. Thepredecoding module 50 converts the digital signal into an encoded signalin accordance with the particular RFID protocol being utilized. Theencoded data is provided to the decoding module 52, which recapturesdata therefrom in accordance with the particular encoding scheme of theselected RFID protocol. The protocol processing module 40 processes therecovered data to identify the object(s) associated with the RFID tag(s)and/or provides the recovered data to the server and/or computer forfurther processing.

The processing module 40 may be a single processing device or aplurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module may have an associatedmemory element, which may be a single memory device, a plurality ofmemory devices, and/or embedded circuitry of the processing module. Sucha memory device may be a read-only memory, random access memory,volatile memory, non-volatile memory, static memory, dynamic memory,flash memory, cache memory, and/or any device that stores digitalinformation. Note that when the processing module 40 implements one ormore of its functions via a state machine, analog circuitry, digitalcircuitry, and/or logic circuitry, the memory element storing thecorresponding operational instructions may be embedded within, orexternal to, the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Further note that,the memory element stores, and the processing module 40 executes, hardcoded and/or operational instructions corresponding to at least some ofthe steps and/or functions illustrated in FIGS. 3-10 below.

FIGS. 3A-3D are schematic block diagrams of an exemplary transmitter 100of the RFID reader in accordance with the present invention. Referringfirst to FIG. 3A, the transmitter 100 includes the processing module 40,the encoding module 42, a combine and adjust power module 140, a powercontroller 130, a synthesizer 110, a local oscillation generator (LOGEN) 120, power amplifiers 150, 152 and 154 and a combining load 160.The power controller 130, combine and adjust power module 140,synthesizer 110, LO GEN 120, power amplifiers 150, 152 and 154 andcombining load 160 form the RF front end 46 of the transmitter 100. Thepower amplifiers 150, 152 and 154 may be linear or non-linear. In FIG.3A, the power amplifiers 150, 152 and 154 have a binary matrix controlwhich enables digitally encoded data to be provided directly to thepower amplifiers 150, 152 and 154. However, in embodiments in which thepower amplifiers 150, 152 and 154 accept analog control input, as shownin FIG. 3B, a DAC 44 is included in the transmit path.

Referring again to FIG. 3A, the processing module 40 provides digitaldata 43 to the encoding module 42 for encoding of the digital data 43 inaccordance with a particular RFID standardized protocol, as discussedabove. In embodiments in which the power amplifiers 150, 152 and 154 arenon-linear, as shown in FIG. 3A, the encoded data 45 is then provided tothe combine and adjust power module 140, where it is combined with anappropriate power variable 135 generated by the power controller 130 toproduce a power-optimized signal 138. The power variable 135 controlsthe individual power produced by each of the power amplifiers 150, 152and 154. The value of the power variable 135 is determined at least inpart by the desired output power of the transmitter, the number of poweramplifiers 150, 152 and 154 and the integrated circuit material on whichthe RFID reader is implemented. For example, if the desired output powerof the transmitter 100 is one watt, a ten volt swing is required acrossone of the power amplifiers 150, 152 or 154. However, in CMOS integratedcircuits, each power amplifier 150, 152 and 154 can tolerate a swing ofonly two volts. Therefore, to produce a total output power of one watt,the power must be divided amongst the power amplifiers 150, 152 and 154such that no power amplifier 150, 152 and 154 has a swing of more thantwo volts. Thus, although not specifically shown, at least five poweramplifiers 150, 152 and 154 would be required to create the desired onewatt output.

As shown in FIG. 3A, the total power is divided evenly between the poweramplifiers 150, 152 and 154, such that each power amplifier 150, 152 and154 receives the same power-optimized signal 138. However, in otherembodiments, the total power may be divided in any manner between thepower amplifiers 150, 152 and 154, as long as the individual powerassociated with each power amplifier 150, 152 and 154 remains withinoperating limits of the integrated circuit material. The outputs 151,153 and 155 of the power amplifiers 150, 152 and 154 are combined by thecombining load 160 to produce the desired total output power of thetransmitter 100.

The frequency synthesizer 110, in combination with the LO GEN 120,generates in-phase (I) and quadrature (Q) RF carrier signals 125(hereinafter termed local oscillation signal) in a desired frequencyband. The frequency band of the local oscillation signal 125 dependsupon the particular RFID standard. For example, various frequency bandsmay include 860-960 MHz, 900-931.3 MHz, 13.56 MHz and 2.45 GHz. As shownin FIG. 3A, the local oscillation signal 125 is input to the poweramplifiers 150, 152 and 154 for amplification and amplitude modulationusing the power-optimized signal 138. The outputs 151, 153 and 155 ofthe power amplifiers 150, 152 and 154 are combined by the combining load160 to produce an outbound RF signal 162 for transmission by the antenna60.

In an exemplary operation involving passive RFID tags, the transmitter100 first transmits an unmodulated, continuous wave (CW) RF signal toactivate and provide power to all passive tags within the range of theantenna 60. To produce the CW signal, the processing module 40 turns onthe power controller 130 and synthesizer 110, but does not provide anydigital data 43 to the encoding module 42. The processing module 40further controls the timing of the power controller 130 and synthesizerto ensure that the CW transmission is long enough to enable the tags toreceive and decode a subsequent interrogation signal from thetransmitter 100 and to generate a response thereto. Thereafter, thetransmitter 100 generates and transmits an amplitude-modulated (AM) RFinterrogation signal to the tags, requesting data from the RFID tags.After the AM signal has been transmitted for a predetermined length oftime, the RF signal is again changed back to a CW signal to providepower to the tags and to allow backscattering of the signal by the tagswith the requested data.

Referring now to FIG. 3C, in embodiments in which the power amplifiers150, 152 and 154 are linear, the analog signal 47 produced by the DAC 47may be mixed with the local oscillation signal 125 at mixer 144 toup-convert the analog signal 47, thereby producing a modulated analogsignal 128. In this embodiment, the modulated analog signal 128 is inputto the power amplifiers 150, 152 and 154 for amplification thereof andthe power variable 135 is provided directly to the power amplifiers 150,152 and 154 to control the output power of each of the power amplifiers150, 152 and 154. In a further embodiment, as shown in FIG. 3D, an I/Qmodulation scheme may be used prior to the power amplifiers 150, 152 and154. For example, such an I/Q modulation scheme may be used for a singlesideband (SSB) transmission from the reader to the tag. Thus, as shownin FIG. 3D, the I and Q components 125 a and 125 b of the localoscillation signal are input to respective mixers 144 a and 144 b formixing with respective I and Q analog signals 47 a and 47 b produced byrespective DACs 44 a and 44 b to up-convert the analog signals 47 a and47 b, thereby producing modulated analog signals 145 a and 145 b.Modulated analog signals 145 a and 145 b are combined at summation node146 to produce combined modulated analog signal 128, which is input topower amplifiers 150, 152 and 154.

FIGS. 4A and 4B are schematic block diagrams of a multi-antennatransmitter 100 of the RFID reader in accordance with the presentinvention. In FIGS. 4A and 4B, instead of using a combining load 160 tocombine the power before transmission, multiple antennas 60 and 62 areused to combine the power over the air interface. Thus, in FIGS. 4A and4B, each antenna 60 and 62 is coupled to a respective power amplifier150 and 152, and each power amplifier 150 and 152 is coupled to arespective combine and adjust power module 140 and 141. In FIG. 4A, thepower amplifiers 150, 152 and 154 have a binary matrix control whichenables digitally encoded data to be provided directly to the poweramplifiers 150, 152 and 154. In FIG. 4B, the power amplifiers 150, 152and 154 accept analog control input, and therefore, DACs 44 and 49 areincluded in the transmit path.

Each combine and adjust power module 140 and 141 is operable to combinethe digital signal 45 with a respective power variable 135 and 137generated by the power controller 130 to produce respectivepower-optimized signals 138 and 139. Each power-optimized signal 138 and139 (digital or analog) is input to a respective power amplifier 150 and152 for modulation and amplification of the RF carrier signals 125generated by the synthesizer 110 and LO GEN 120 to produce respectiveamplified partial outbound RF signals 151 and 153. Each amplifiedpartial outbound RF signal 151 and 153 is directed to a respectiveantenna 60 and 62 for transmission and power combining over the airinterface. In other embodiments, each power amplifier 150 and 152 isformed of multiple power amplifiers in the configuration shown in FIG.3.

In one embodiment, the antennas 60 and 62 form an antenna array capableof supporting beamforming and/or polarization (e.g., circularpolarization or hopping polarization). For example, as shown in FIGS. 4Aand 4B, a phase distribution controller 170 is operably coupled toreceive the local oscillation signal 125 from the LO GEN 120. The phasedistribution controller 170 controls the individual phases of theantennas 60 and 62 by producing respective phase-controlled RF signals172 and 174 to the power amplifiers 150 and 152. By controlling thephases of the RF signals output by each antenna 60 and 62, variousbeamforming and polarization techniques may be used.

FIG. 5 is a schematic block diagram of a receiver 200 of the RFID readerin accordance with the present invention. The receiver 200 includes lownoise amplifiers 210 and 212, a block cancellation module 220, adown-conversion module 230, a receiver local oscillation (LO) controller250, the digitization module 48, the pre-decoding module 50, thedecoding module 52 and the processing module 40. The LNAs 210 and 212,block cancellation module, down-conversion module 230 and controller 250form the RF front end 46 of the receiver 200. Each low noise amplifier210 and 212 is operably coupled to receive a respective inbound RFsignal 202 and 204 from a respective antenna 60 and 62 and to amplifythe inbound RF signals 202 and 204 to produce respective amplifiedinbound RF signals 216 and 218.

Since the carrier frequency of the inbound RF signal is substantiallysimilar to the carrier frequency of the outbound RF signal, each inboundRF signal 202 and 204 may include not only a modulated inbound RF signalfrom an RFID tag, but also a blocking signal resulting from leakage ofthe outbound RF signal from the transmitter 100 into the receiver 200.For example, in embodiments utilizing passive tags, as described above,the RFID reader transmits an unmodulated, continuous wave (CW) signal topower the RFID tag and allow for backscattering of the RF signal. ThisCW signal may block or otherwise mask the inbound modulated RF signalreceived from the RFID tag. To identify the desired inbound modulated RFsignal from an RFID tag, the amplified inbound RF signals 216 and 218are input to the block cancellation module 220. The block cancellationmodule 220 substantially cancels the blocking signal from the amplifiedinbound RF signals 216 and 218 and substantially passes the modulated RFsignal 222 by subtracting the outbound RF signals 151 and 153 producedby the transmitter 100 from the amplified inbound RF signals 216 and218.

To effectively cancel the blocking signal from the amplified inbound RFsignals 216 and 218, referring again to FIGS. 3A-3D and 4A and 4B, theoutbound RF signal is tapped from either the output (e.g., 151-155) ofthe power amplifier 150 or the input (e.g., 125, 128 or 170-172) of thepower amplifier 150 and provided to the input of the receiver LOcontroller 250, as shown in FIG. 5. In embodiments in which the outboundRF signal is taken from the output of the power amplifier 150, such anarchitecture compensates for any phase noise in the outbound RF signalproduced by the power amplifier 150. In embodiments in which multiplepower amplifiers drive a single antenna or multiple antennas, and theoutputs are tapped, the outputs 151-155 of each of the power amplifiers150-154 are input to the receiver LO controller 250 and combined forinput to the block cancellation module 220. In embodiments in whichmultiple power amplifiers drive multiple antennas, and the inputs of thepower amplifiers are tapped, as shown in FIGS. 4A and 4B, the inputs172-174 of each of the power amplifiers 150-152 are input to thereceiver LO controller 250 and combined for input to the blockcancellation module.

The receiver LO controller 250 is further operably coupled to receivethe local oscillation signal 125 generated by the LO GEN 120 and toinput the local oscillation signal to the down-conversion module 230.The down-conversion module 230 includes a pair of mixers 240 and 242 tomix the inbound modulated RF signal with the local oscillation signal toproduce analog near baseband signals. The digitization module 48converts the analog near baseband signals to digital baseband signals.The digitization module 48 may be an analog-to-digital converter or alimiter. The predecoding module 50 converts the digital baseband signalsinto an encoded signal in accordance with the particular RFID protocolbeing utilized. The encoded data is provided to the decoding module 52,which recaptures data therefrom in accordance with the particularencoding scheme of the selected RFID protocol and provides the recovereddata to the processing module 40. Although the receiver LO controller250 is shown receiving both the local oscillation signal 125 from the LOGEN 120 and the input/output of the power amplifier 150, in otherembodiments, the receiver LO controller 250 receives only one of thesesignals (i.e., either the local oscillation signal 125 or theinput/output of the power amplifier) and provides this single receivedsignal to both the down-conversion module 230 and the block cancellationmodule 220.

FIG. 6 is a diagram illustrating an example of the functionality of theblock cancellation module 220 of FIG. 5. The block cancellation module220 includes a combiner 310, a controller 320 and a carrier injectionmodule 330. The combiner 310 is operably coupled to receive theamplified inbound RF signals 216 and 218 from the low noise amplifiersand to combine the amplified inbound RF signals 216 and 218 to produce acombined inbound RF signal 312. The combined inbound RF signal 312 isinput to the carrier injection module 330 to substantially cancel anyblocking signal from the combined inbound RF signal 312 andsubstantially pass the inbound modulated RF signal 222 within thecombined inbound RF signal 312 that is produced by the RFID tag.

The carrier injection module 330 includes a subtraction module 340 and aparameter estimator module 350 operably coupled in a feedback loop tothe controller 320. The subtraction module 340 is operably coupled toreceive the combined inbound RF signal 312 from the combiner 310 and acancellation signal 324 from the controller 320. The subtraction module340 subtracts the cancellation signal 324 from the combined inbound RFsignal 312 to produce the inbound modulated RF signal 222.

The cancellation signal 324 is generated by the controller 320 inresponse to input from the receiver LO controller, a feedback signal 355generated by the parameter estimator module 350 and a control signal 322generated by the processing module. The control signal 322 indicateswhether a blocking signal may be present in the combined inbound RFsignal, and as such, whether block cancellation needs to be performed.If the control signal 322 requests the controller 320 to perform blockcancellation, the controller 320 initially determines the phase andamplitude of the cancellation signal 324 from the outbound RF signal(e.g., signals 151 and 153) generated by the transmitter and input tothe controller 320 from the receiver LO controller. Thereafter, thecontroller 320 continually adjusts the phase and amplitude of thecancellation signal 324 in response to the feedback signal 355. Thefeedback signal 355 includes phase and/or amplitude estimationsperformed on the modulated RF signal 222 by the parameter estimationmodule 350.

FIGS. 7A and 7B are schematic block diagrams of a dual-mode RF front end46 of the RFID reader in accordance with the present invention. In FIGS.7A and 7B, the dual-mode RF front end 46 includes a near-field module400 for operating in a near-field mode and a far-field module 450 foroperating in a far-field mode. The near-field module 400 includes apower amplifier 410, a low noise amplifier 420 and a coil 430. Thefar-field module 450 includes a power amplifier 150, a low noiseamplifier 140 and antennas 60 and 62. Switches 222, 224 and 226 controlthe operation of the RF front-end 46 in either near-field mode orfar-field mode.

In near-field mode, an analog signal from the baseband processor isprovided by switch 226 to the near-field module 400. The analog signalis mixed with a local oscillation signal produced by synthesizer 110 andinput to power amplifier 410 for amplification thereof. The amplifiedsignal induces the coil 430 to produce a magnetic field which couples tothe RFID tag coil through mutual inductance, thereby initiatingoperation of the tag. The tag generates and transmits an RF responsesignal to the RFID reader through mutual inductance in the same manneras described above. Typically, the tag utilizes frequency or amplitudemodulation of the response signal to encode data stored in the tag intothe response signal.

When the tag response signal couples to the reader coil 430, the RFresponse signal is received at the low noise amplifier 420 and passed tothe block cancellation module 220 via switch 224 for further processing.While in near-field mode, the outbound RF signal is tapped from eitherthe input of the power amplifier 410, as shown in FIG. 7A, or the outputof the power amplifier 410, as shown in FIG. 7B, and input via switch222 to the block cancellation module 220 for cancellation of theblocking signal in the RF response signal provided by the LNA 420. Theoutput of the block cancellation module 220 is input to thedown-conversion module 230, as described above.

In far-field mode, an analog signal from the baseband processor isprovided by switch 226 to the far-field module 450. The analog signal ismixed with a local oscillation signal produced by synthesizer 110 andinput to power amplifier 150 for amplification thereof, as shown inFIGS. 3C-3D. In other embodiments, the analog or a corresponding digitalsignal is used to modulate the local oscillation signal at the poweramplifier 150, as shown in FIGS. 3A-3B and 4A-4B. The amplified signalis transmitted by antenna 60 to all tags within the range of antenna 60.

Each tag within range of the antenna 60 generates and transmits an RFresponse signal to the RFID reader through backscattering, as describedabove. The RF response signal is received by antenna 62 and passed tothe low noise amplifier 420 for amplification thereof. The amplified RFresponse signal is provided to the block cancellation module 220 viaswitch 224 for further processing. While in far-field mode, the outboundRF signal is tapped from either the output of the power amplifier 150,as shown by a solid line, or from the input of the power amplifier 150,as shown by a dotted line, and input via switch 222 to the blockcancellation module 220 for cancellation of the blocking signal in theRF response signal provided by the LNA 140. The output of the blockcancellation module 220 is input to the down-conversion module 230, asdescribed above.

FIG. 8 is a schematic block diagram of a multi-band synthesizer 110 ofthe RFID reader in accordance with the present invention. The multi-bandsynthesizer 110 includes a voltage controlled oscillator (VCO) 520, ahopping sequence generator 510, a divide-by-2 block 530, a divide-by-8block 560, a filter 550, multipliers 540 and 570 and a direct digitalfrequency synthesizer (DDFS) 580. The hopping sequence generator 510controls the frequency output of the VCO 520. The frequency produced bythe VCO 520 is input to the divide-by-2 block 530 and multiplied bymultiplier 540 to the output of the divide-by-2 block 530. The output ofthe multiplier 540 is input to the filter 550, and the output of thefilter 550 is input to the divide-by-8 block 560. The output 565 of thedivide-by-8 block 560 is input to the multiplier 570 for multiplicationwith the output of the DDFS 580.

The divide-by-8 block 560 and DDFS 580 allows the synthesizer 110 toeasily generate in-phase (I) and quadrature (Q) carrier signals in threedifferent frequency bands. For example, RF carrier signals 565 in afirst frequency band (e.g., 900-931.3 MHz) are produced by taking theoutput of the divide-by-8 block 560, RF carrier signals 575 in a secondfrequency band (e.g., 860-960 MHz) are produced by taking the output ofthe multiplier 570 and RF carrier signals 585 in a third frequency band(e.g., 13.56 MHz) are produced by taking the output of the DDFS.

FIG. 9 is a functional diagram of a multi-standard processing module 40of the RFID reader in accordance with the present invention. Theprocessing module 40 includes reader drivers 610, a reader controller620 and a memory 630. The memory 630 maintains various RFID standardizedprotocols 640 and 642. The reader controller 620 is operably coupled tothe memory 630 to access and retrieve protocol information for executingthe protocols 640 and 642. The protocol information includesinstructions for the reader controller 620 to program the RF front end46, the encoding module 42 and the decoding module 52, the latter twobeing shown in FIG. 2.

In FIG. 9, the encoding module 42 is represented by encoding blocks 650and 652 and the decoding module 52 is represented by decoding blocks 660and 662. Encoding block 650 and decoding block 660 represent theencoding module 42 and decoding module 52, respectively, as programmedfor a first protocol 640, whereas encoding block 652 and decoding block662 represent the encoding module 42 and decoding module 52,respectively, as programmed for a second protocol 642.

The reader controller and memory 630 are further operably coupled to thereader drivers 610 to communicate with a host device via the hostinterface 64. For example, the host device may download protocolinformation to the memory 630 via the host interface 64 and readerdrivers 610. As another example, the host device may instruct the readercontroller 620 to search for active and/or passive tags within thecoverage area of the reader via the host interface 64 and reader drivers610. In an exemplary operation, if the reader controller 620 is notprovided with a particular protocol for the tag search, the readercontroller 620 may initiate a protocol scan to identify the protocolsassociated with each tag within the coverage area of the reader. Fromthe protocol scan, the reader controller 620 can determine thepercentage of tags supporting each protocol for use in schedulingcommunications between the reader and the tags.

FIG. 10 is a logic diagram of a method 700 for operating the integratedRFID reader in accordance with the present invention. The method beginsat step 710, where an outbound RF signal is generated by the RFIDreader. The outbound RF signal is a request for identification data fromone or more RFID tags within the coverage area of the RFID reader. Theprocess then proceeds to steps 720 and 730 where the RFID readerreceives an inbound RF signal from one or more tags and amplifies theinbound RF signal. The frequency of the inbound RF signal issubstantially similar to the frequency of the outbound RF signal. Theinbound RF signal includes at least a modulated RF signal produced byone of the tags in response to receipt of the outbound RF signal by thetag. The inbound RF signal may further include a blocking signalcorresponding to the outbound RF signal, and resulting from leakage ofthe outbound RF signal from the RFID transmitter to the RFID receiver.

The process then proceeds to step 740 where the blocking signal issubstantially canceled from the inbound RF signal to substantiallyisolate the modulated RF signal from the RFID tag. For example, in oneembodiment, the blocking signal is canceled by subtracting the outboundRF signal produced by the transmitter from the inbound RF signal(amplified or not amplified). Once the blocking signal has beensubstantially canceled from the inbound RF signal, the process continuesat steps 750-770 where the isolated modulated RF signal from the RFIDtag is converted to a near baseband signal, the near baseband signal isconverted to a digital signal and the digital signal is converted intodigital symbols representing the requested identification data of theRFID tag.

As one of ordinary skill in the art will appreciate, the term“substantially,” as may be used herein, provides an industry-acceptedtolerance to its corresponding term and/or relativity between items.Such an industry-accepted tolerance ranges from less than one percent totwenty percent and corresponds to, but is not limited to, componentvalues, integrated circuit process variations, temperature variations,rise and fall times, and/or thermal noise. Such relativity between itemsranges from a difference of a few percent to magnitude differences. Asone of ordinary skill in the art will further appreciate, the term“operably coupled”, as may be used herein, includes direct coupling andindirect coupling via another component, element, circuit, or modulewhere, for indirect coupling, the intervening component, element,circuit, or module does not modify the information of a signal but mayadjust its current level, voltage level, and/or power level. As one ofordinary skill in the art will also appreciate, inferred coupling (i.e.,where one element is coupled to another element by inference) includesdirect and indirect coupling between two elements in the same manner as“operably coupled”.

The preceding discussion has presented an integrated, low-cost RFIDreader and method of operation thereof. As one of ordinary skill in theart will appreciate, other embodiments may be derived from the teachingof the present invention without deviating from the scope of the claims.

1. A reader for a radio frequency identification system, comprising: atransmitter operable to generate an outbound radio frequency (RF)signal; a receiver operable to receive an inbound RF signal having afrequency similar to a frequency of said outbound RF signal, saidinbound RF signal including a blocking signal corresponding to saidoutbound RF signal and a modulated RF signal produced responsive to saidoutbound RF signal, said receiver comprising: a low noise amplifieroperably coupled to amplify said inbound RF signal to produce anamplified inbound RF signal, a block cancellation module operablycoupled to receive said outbound RF signal from said transmitter and tosubstantially cancel said blocking signal from said amplified inbound RFsignal using said outbound RF signal and substantially pass saidmodulated RF signal, a down-conversion module operably coupled toconvert said modulated RF signal to a near baseband signal, and adigitizing module operably coupled to convert said near baseband signalinto a digital baseband signal; and a processing module operably coupledto convert said digital baseband signal into inbound digital symbols. 2.The reader of claim 1, wherein said reader is integrated on a singlechip.
 3. The reader of claim 1, wherein said transmitter comprises afirst power amplifier operably coupled to amplify said outbound RFsignal, and wherein said block cancellation module is operably coupledto receive said outbound RF signal from an output or an input of saidfirst power amplifier, and further including: an antenna operablycoupled to receive said outbound RF signal and transmit said outbound RFsignal.
 4. The reader of claim 3, wherein said transmitter comprises asecond power amplifier operably coupled to receive said outbound RFsignal and produce an amplified outbound RF signal, and wherein saidblock cancellation module is operably coupled to receive said outboundRF signal from an input or an output of said second power amplifier, andfurther including: a coil operably coupled to receive said amplifiedoutbound RF signal and transmit said amplified outbound RF signal bygenerating and modulating the strength of a magnetic field.
 5. Thereader of claim 1, wherein said outbound RF signal is a modulated RFsignal during a first time period and an unmodulated continuous wave RFsignal during a second time period.
 6. The reader of claim 1, whereinsaid reader is implemented in a CMOS integrated circuit, and whereinsaid transmitter further comprises: multiple power amplifiers, eachoperably coupled to receive a respective partial outbound RF signal andto amplify said respective partial outbound RF signals to producecorresponding amplified partial outbound RF signals; and a powercontroller operably coupled to control the power of each of said poweramplifiers to within a limit of said CMOS integrated circuit.
 7. Thereader of claim 6, wherein said transmitter further comprises: acombining load operably coupled to combine said amplified partialoutbound RF signals to produce said outbound RF signal.
 8. The reader ofclaim 6, wherein said transmitter further comprises: an antenna arrayincluding multiple antennas, each operably coupled to receive arespective amplified partial outbound RF signal and to transmit saidrespective amplified partial outbound RF signal for combination of saidamplified partial outbound RF signals over an air interface to producesaid outbound RF signal.
 9. The reader of claim 8, wherein saidtransmitter further comprises: a phase distribution controller operablycoupled to said power amplifiers to control a respective phase of eachof said amplified partial outbound RF signals.
 10. The reader of claim8, wherein each of said multiple power amplifiers further comprises:multiple power amplifiers, each operably coupled to receive a respectivesub-partial outbound RF signal and to amplify said respectivesub-partial outbound RF signals to produce corresponding amplifiedsub-partial outbound RF signals; and a combining load operably coupledto combine said amplified sub-partial outbound RF signals to producesaid respective amplified partial outbound RF signal.
 11. The reader ofclaim 6, wherein said power amplifiers are non-linear, and wherein saidpower controller is further operable to modulate the power provided toeach of said power amplifiers to produce an amplitude-modulated outboundRF signal.
 12. The reader of claim 1, wherein said digitizing module isa limiter or an analog-to-digital converter.
 13. The reader of claim 1,wherein said block cancellation module comprises: a controller operablycoupled to receive said outbound RF signal and to produce a cancellationsignal from said outbound RF signal; a carrier injection module operablycoupled to receive said inbound RF signal and said cancellation signaland to substantially cancel said blocking signal and substantially passsaid modulated RF signal using said cancellation signal; and a feedbackloop operably coupled to control said cancellation signal from saidmodulated RF signal.
 14. The reader of claim 1, further comprising: ahost interface operably coupled to interface said reader with a hostdevice.
 15. The reader of claim 1, further comprising: a frequencysynthesizer operable to produce signals at multiple frequencies andoperably coupled to said transmitter to generate said outbound RF signalat one of said multiple frequencies.
 16. The reader of claim 1, whereinsaid processing module is programmed with multiple protocols, andwherein said processing module converts said digital baseband signalinto said digital symbols using a select one of said protocols.
 17. Amethod for operating an integrated reader for a radio frequencyidentification system, comprising: generating an outbound radiofrequency (RF) signal; receiving an inbound RF signal having a frequencysimilar to a frequency of said outbound RF signal, said inbound RFsignal including a blocking signal corresponding to said outbound RFsignal and a modulated RF signal produced responsive to said outbound RFsignal; amplifying said inbound RF signal to produce an amplifiedinbound RF signal; substantially cancelling said blocking signal fromsaid amplified inbound RF signal using said outbound RF signal tosubstantially pass said modulated RF signal; converting said modulatedRF signal to a near baseband signal; converting said near basebandsignal into a digital baseband signal; and converting said digitalbaseband signal into inbound digital symbols.
 18. The method of claim17, wherein said outbound RF signal is a modulated RF signal during afirst time period and an unmodulated continuous wave RF signal during asecond time period.
 19. The method of claim 17, wherein said generatingfurther comprises: receiving partial outbound RF signals; amplifyingeach of said respective partial outbound RF signals to producecorresponding amplified partial outbound RF signals; and combining saidamplified partial outbound RF signals to produce said outbound RFsignal.
 20. The method of claim 19, wherein said generating furthercomprises: controlling a respective phase of each of said amplifiedpartial outbound RF signals.
 21. The reader of claim 17, wherein saidgenerating further comprises: modulating the power of each of saidamplified partial outbound RF signals to produce an amplitude-modulatedoutbound RF signal.